The present invention relates generally to air-fuel controls for internal combustion engines and, more particularly, to a system for controlling air-fuel ratio during intake control device transitions.
Under steady-state engine operating conditions, the mass of air charge for each cylinder event is constant and the fuel transport mechanisms in the fuel intake have reached equilibrium. As a result, the mass of injected fuel for each cylinder event is also constant. When the operating condition is not steady-state, however, the mass of injected fuel required to achieve the desired air-fuel ratio in the cylinder is not constant. Transient operation can be due to changes in the mass of air charge, less than all of the cylinders being fueled for each event, or a desired change in the air-fuel ratio.
U.S. Pat. No. 5,746,183 describes a system for controlling fuel delivery during transient engine conditions using a series of steps. This method accomplishes improved fuel delivery by sensing a plurality of engine parameters. The method described includes the step of determining an initial base desired fuel mass based on the plurality of engine parameters. The method further includes the step of determining an initial transient fuel mass based on the prior injection history. Still further, the method includes the step of determining a desired injected fuel mass to be delivered to the individual cylinder based on the initial base desired fuel mass and the initial transient fuel mass. Finally, the method includes the step of sensing delivery of the desired injected fuel mass and determining an updated prior injection history based on the desired injected fuel mass and the prior injection history.
In engines equipped with intake manifold runner control (IMRC) systems, however, additional air-fuel control mechanisms may be required. In particular, during IMRC transitions when the engine is cold, the engine""s air-fuel ratio goes lean on transitions to open the valve, and rich on transitions to close the valve. This can result in an undesirable torque xe2x80x98bumpxe2x80x99 relating to air-fuel ratio control.
Thus, there exists a need to improve air-fuel control during intake control device transitions by compensating for fuel transport dynamics and the actual fuel injected into each cylinder.
It is an object of the invention to provide an improved and reliable means for controlling air-fuel ratio during intake control device transitions. Another object of the invention is to minimize lean air-fuel excursions during accelerations. An additional object of the invention is to minimize rich air-fuel excursions during decelerations.
In carrying out the above object and other objects, features, and advantages of the present invention, a method is provided for determining the fuel mass to be delivered to a cylinder during transient engine conditions caused by intake control device transitions. The method includes the step of sensing a plurality of engine parameters. The method also includes the step of determining an initial base desired fuel mass based on the plurality of engine parameters. The method further includes the step of determining an initial transient fuel mass based on the prior injection history, which is modified as a function of the intake control device transition. Still further, the method includes the step of determining a desired injected fuel mass to be delivered to the individual cylinder as a function of the initial base desired fuel mass and the initial transient fuel mass. The method further includes the step of sensing delivery of the desired injected fuel mass and determining an updated prior injection history as a function of the desired injected fuel mass and the prior injection history.
In further carrying out the above object and other objects, features, and advantages of the present invention, a system is also provided for carrying out the steps of the above described method. The system includes a plurality of sensors for sensing a plurality of engine parameters. The system also includes control logic operative to determine an initial base desired fuel mass as a function of the plurality of engine parameters and determine an initial transient fuel mass based on the prior injection history. The prior injection history is modified as a function of the intake control device transient. The system further includes control logic to determine a desired injected fuel mass to be delivered to the individual cylinder as a function of the initial base desired fuel mass and the initial transient fuel mass, and sense delivery of the desired injected fuel mass to the individual cylinder. The system further determines an updated prior injection history as a function of the desired injected fuel mass and the prior injection history.
The present invention achieves an improved and reliable means for controlling air-fuel ratio during intake control device transitions. Also, the present invention is advantageous in that it will overcomes the problem of torque xe2x80x98bumpxe2x80x99 associated with cold engines.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.